Roger's RRC: An update

[Bo]

I didn't realise you were building Knight-Rider!
http://www.youtube.com/watch?v=Mo8Qls0HnWo

[davew]

Just as an aid to diagnosis and to try and verify if the problem is actually the LPG system. What happens when you run it on petrol in the same scenario ?

How air tight is your exhaust system, particularly between the lambda sensor and the cylinder head ?

Is the lambda sensor heated and how far away from the cylinder head is it ?

If heated have you verified the heater circuit is working OK ?

Is the lambda sensor on one bank or both (before or after the Y piece) ?

[TwoSheds]

I didn't realise you were building Knight-Rider!
http://www.youtube.com/watch?v=Mo8Qls0HnWo

I thought exactly that when I saw it! I never expected it to be so bling - after reading about Lambda sensors 'flipping' and knowing that there is next to no damping or delay in the indicator I thought it would be just the two end lights coming on. I must admit I am secretly quite pleased with the result...

What happens when you run it on petrol in the same scenario ?

Very similar - indicates lean most of the time while cruising, but flips up and down while normal driving (which the LPG doesn't) I tried fiddling with the adjuster screw on the AFM, but not sure if mine is connected to anything - it just goes round and round and doesn't seem to ever have an effect... One thing (on petrol) that is a bit strange is that there appears to be no enrichment when opening the throttle suddenly - possibly indicating a fault in the TPS circuit, but since I never run on petrol (except when I have run out of gas) I haven't spent any time on this.

How air tight is your exhaust system, particularly between the lambda sensor and the cylinder head ?

Not really sure - should be ok, can't hear or feel anything - but both petrol and LPG can indicate rich (petrol quite often) so hopefully that's ok, but maybe that's too simplistic (typical me). Actually - having said that about not hearing anything, there is a slightly strange noise (a bit like quiet pinking, but not pinking) that only occurs when the engine is cold and accelerating at about 2400rpm, I guess that could be a manifold leak which is self-sealing to a degree once the manifold gets hot? But then if it is self sealing it shouldn't affect the Lambda readings anyway. hmmm

Is the lambda sensor heated and how far away from the cylinder head is it ?
If heated have you verified the heater circuit is working OK ?
Is the lambda sensor on one bank or both (before or after the Y piece) ?

The heater is working well or was when I put it in (ouch!) and it's mounted on one branch of the Y about 12-15" from the manifold joint. Not ideal I know, but not bad I thought.

So far I have 'calibrated' it by running on petrol and adjusting until the whole range of LEDs are capable of being lit up during normal driving (it is supposed to be a 0-1v meter, with the 1v end is adjustable, but the adjustments affect each other and I am not entirely sure that the zero end is actually zero, or that it stays still when the 1 end is being adjusted...)

Assuming the LEDs are numbered 1 (lean) to 10 (rich): If I start it from cold on petrol it will fire up with the 1 lit (the heater takes time) and will then rise over a few tens of seconds until it's dancing around the green bit, so from that I am assuming that it's not a million miles out, although of course my car is open-loop even on petrol so I can't really be sure.

Of course my home-brew ignition map may also be having a deleterious effect here too. One day when I have some spare cash (hah!) I need to get it on a rolling road... In the mean time - it feels to be running quite well although it's rather heavy on fuel - running at about 10mpg on gas.

Ah well - I'll keep plugging on - one day I will get there, but in the mean time I enjoy messing with it so no big problem

Thanks for the Q's Dave - you made me think and have given me some fresh directions.

Roger

[TwoSheds]

Stupid stupid stupid stupid stupid stupid

When I came to put the OSR hub together about two years ago I found that in my bag of bits I been given the wrong locking washer - I had a tab type instead of a D type - no probs I thought - I'll fit it anyway and just cut off the tab and replace it when I get a round tuit. Well of course I never did get that round tuit and so today I started getting some nasty noises from the rear, and sure enough the nuts - although still locked together, had moved and allowed a couple of mm of free play in the bearing.

Luckily the bearing it's self is fine and when tightened up a bit runs smoooth and easy - lucky me!

As it happens, the BMW has also been sidelined by a baggy OSR wheel bearing (Is somebody trying to tell me something?) and so it's public transport tomorrow and hopefully four plus four (which is within walking distance of my office) will have the bits I need. At least with the Range Rover it's a DIY job - unlike the BMW...

[TwoSheds]

OK - so the OSR bearing was quite loose but spinning smoothly. The NSR had only a little play and seemed fine.
Skived off work for an hour this morning to adjust them and the left one is great - did up nicely and took out all the play.

But - The right one is...'funny'. If I try to put even a small amount of torque on the inner nut (just my hand on the box spanner) it gets very stiff to turn the wheel (but still smooth). Anyway - I have put it back with a tiny amount of play and it spins smooth enough, but just done a run (6 miles at 50mph) and checked and the NSR hub (the good one) is cool but the OSR hub is warm. I don't have time to investigate further right now since the RRC has become my DD.

I have never know a bearing 'go' while still being smooth, but I am thinking that's what happened - any comments would be appreciated...

[TwoSheds]

Since the RRC is now my DD - I have finally got round to putting the old alloys and AT tyres back on it - these wheels/tyres have not been used or checked since the days of the golden Disco - what - 4 years? Anyway - three were ok but one was about 4psi down. Anyone know where I complain to about this?

Anyway - now with ATs on which are a good bit smaller too, I went out for a test drive: Grip, cornering, NVH, responsiveness - all a lot better. Funny thing though is braking - on the old MTs I could howl them to a halt without locking more than momentarily - with these they grip really well but then let go suddenly and completely making me feel a lot more uneasy about heavy braking. It also looks stupid too

[davew]

Putting larger diameter tyres on decreases your available braking force.

Conversely, after changing back to smaller diameter tyres, it will take less pressure on the pedal to get the same braking force at the contact patch whilst at the same time reducing the size of the contact patch. The combination of the two, even when moving to a more road biassed tread pattern, makes it much more likely that you will lock it up.

[TwoSheds]

Been Rsing around with the mixture recently and this weekend I went to the Lake District and back with MT's on and averaged 15mpg on gas. That may not sound much but on the last measured run to Bonsall and back (on ATs), I only managed 10mpg. Hopefully if I mess around some more I might improve it again by 50% and be up to 22.5mpg - or not

[TwoSheds]

Arsing around again - I thought (after reading a post on another forum) that I should make an overrun fuel cut-off for the LPG. Now this is particularly easy since I have MegaJolt which gives outputs based on either revs or manifold pressure.
So first I did a proof of concept - I put a switch in line to the LPG cut-off solenoid (the one on the vapouriser so it was as close as possible to the inlet) and experimented: I tried switching off the gas if the revs are above 1200rpm AND the MAP is less than 20 KPa - ie when the engine is on the overrun. It worked beautifully!
So I wired in a solenoid and it's useless..

The problem is that there is no hysteresis in the signal/switching and so as the car slows it comes to the point where the MAP gets low enough (due to falling revs) to switch the gas back on, and from there it's on-off-on-off twice a second for several seconds until it gets through the transition zone.

Anyone know how to sort this (introduce hysteresis) or perhaps just delay the switching off for a second or so? I reckon that there should be a way by putting a bit of a capacitor in the circuit, but I can't work it out...

Roger

[davew]

The infamous 555 timer would make it fairly simple to set up a circuit with an adjustable time delay before the fuel shuts off, assuming your MJ outputs are going low when you want to turn the gas off.

As it's just using a capacitor/resistor charge/discharge circuit and turning that into a logic output you can set both a delay before the gas turns off and also a different delay before the gas turns on again.

[TwoSheds]

Google!

[TwoSheds]

Google!

hmmmmm... Not as easy as I had hoped - maybe a project for darker evenings

Thanks for the suggestion Dave - it certainly looks like a 555 is the way to go. The nice thing about my proposed setup is that at any time I can merely reconnect the original wire and take any mods out of the circuit, so the additional complexity is not going to affect reliability (not while I own the car anyway - god help anyone else who tries to work out the wiring...

Roger

[TwoSheds]

At last - after 4 years of promising to buy myself a set of tyres -I've got some:

[davew]

What did you do with the Machos ?

Could really do with another one as a stop gap atm !

[TwoSheds]

What did you do with the Machos ?

Could really do with another one as a stop gap atm !

I'll bring them this weekend if you like?

If you don't want them all I wouldn't mind keeping one as a spare?